Lens grinding tool and method



Feb. 13, 1951 A. J. HoLMAN 2,541,873

LENS GRINDING TOOL AND METHOD Filed April 24, 1945 2 Sheets-Sheet 1 nume FIG. I

. v as Flcaz \lts ARTHUR LHOLMAN 1 INVENTOR ATTORNEY Feb. 13, 1951 A. J. HoLMAN 2,541,873

LENS GRINDING TOOL AND METHOD Filed April 24, 1945 2 sheets-sheet@ FIG. 3

A'I'I'ORNEY Patented Feb. 13, 1951 UNITED STATES PATENT OFFICE 2,541,873 LENS GRINDING TooL AND METHOD Arthur J. Holman, Brighton, N. Y. y

Application April 24, 1945, Serial No. 589,983 4 claims. (c1. si-zw This invention relates to lens grinding apparatus and methods and, more particularly, to tool means and grinding methods as applied in generating curved surfaces on lens blanks, one object of the invention being to provide an improved generating method whereby surfaces are both rough and nish ground successively and simultaneously during a single passage of the lens blanks across the grinding rings.

Another object is the provision of improved generating tool means for carrying out the above method by continuous relativev movement of the tool means and lens blank.

Another object is to provide an improved to o1 means of the above character in a simple and practical type of construction capable of being readily and conveniently adapted to various working requirements and of operating rapidly and with a high degree of precision. i

To these and other ends the invention resides in certain improved method steps and parts and combinations thereof, all as will be hereinafter more fully described, the novel features being pointed out in the claims at the end of the specication.

In the drawings:

Fig. 1 is a top plan view of an apparatus embodying and for carrying .out the present invention;

Fig. 2 is an elevation of the same as viewed from the right in Fig. 1;

Fig. 3 is a sectional elevation substantially on the line 3a--3a in Fig. 1, and

Fig. 4 is an enlarged sectional detail view of parts shown in Fig. 3.

The invention is embodied and carried out in the present instance by a tool means adapted for use in a convex spherical generating machine, such as disclosed and claimed in the copending application of Arthur J. Holman and William J. Kennedy, Serial No. 583,244, filed March 17, 1945, which issued as Patent No. 2,510,113 on June 6, 1950, for Method and Machine for Grinding Lenses, although the invention is applicable las well to other types of machines..

The present embodiment preferably comprises a standard I having a bifurcated upper end formed with spaced bearings, I I and I2, rotatably supporting a trunnion I3 carried by and supporting a tool holder I4 of hollow hemispherical shape. Trunnion I3 has fixed .thereon between its bearings a pulley I5 driven by a belt I6 for rotating the tool holder at suitable grinding speed.

The tool holder is formed at its rim with an annular surface I1 preferably lying in a plane normal to the axis of rotation of the holder inv bearings II and I2. Surface I1 forms a seat for the tool means proper comprising a plurality of grinding elements or rings made of abrasive materials of different degrees of coarseness, respectively, and formed on their inner peripheries with circular abrading surfaces centered on the tool holder axis for successively engaging a lens blank fed transversely ofthe abrading surfaces, the lens blank being mounted on the periphery of a carrier Wheel rotating about an axis intersecting perpendicularly the rotary axis of the tool holder I4 and lying in the plane of the tool seat I1, as hereafter more fully described.

Inconnection with a machine of the present type for generating convex lenses, 'the grinding tool has seated on the surface I I an annular ring I8 made of diamond abrasive material adapted for the ilnish grinding of the blank, such, for example, as No. 400 grit, the circular inner peripheral edge of the ring being also curved transversely about the axis of the blank carrier. Located in concentric, side by side relation with the ring I8 is a` second grinding ring I9, of the same construction, but made of a coarser diamond 26 abrasive material such, for example, as No. 120

grit, the inner peripheral grinding edge of ring I 9 being located at a greater radial distance from the tool axis than the grinding edge 'of ring I8. An annular spacing member or ring 20 is preferably interposed between rings I8 and I9 so as to space their abrading surfaces longitudinally of the tool axis and leave an annular recess 2| therebetween to provide a channel for the circulation of suitable liquidA coolant for scavenging chips, grit and the like, removed by the grinding operation. Such coolant is supplied through connections comprising a, bore in trunnion I3 communicating with channels in tool holder I4, as shown, which register with openings 39 through the inner ring I8 and with vent openings 40 through the ring 20, leading to the recess 2|. An annular cover plate 22 is preferably placed over the outer ring I9, and the several tool parts are detachably secured together and to the holderby means of screws 23 passing through openings therein and entering tapped holes in the rim of the holder as shown. While but two grinding rings are shown in the present instance, it is obvious that additional rings may be employed by extension of the same construction.

The means for feeding a lens blank into cutting cooperation with a tool such as described comprises, in the present instance, a carrier wheel 24, having formed in its periphery a series of cylindrical sockets 25, for the reception of lens blank chucks 26, of the usual, or any suitable asuste construction, formed with recessed seats 21 in which the lens blanks 28 are secured, as well understood in'the art. Each chuck is preferably formed with a circumferential groove 29 for engagement with a spring actuated plunger 30 located in an inclined bore 3| in the wheel for detachably holding the chuck seated in its socket and so that it may be manually detached during the feeding rotation of the wheel for removing ground blanks and substituting new blanks to be ground, as more fully described in the copending patent application referred to above.

The sockets 25 and chucks 26 are accurately positioned on the carrier wheel so that their axes lie in a common plane perpendicular to the axis of rotation of the wheel at its intersection with the tool axis, and the Wheel is supported in the above described relation to the tool by means of trunnions 32 and 33, extending from opposite sides of the wheel and rotatably mounted in bearings in spaced arms 34 and 35 extending from the forked upper end of a standard 3.3 fixed to the same machine frame or other support as the tool standard l0.

Wheel trunnion 33 is preferably extended to receive a worm wheel 31 fixed thereon and meshing with a worm 38 for rotating the wheel at suitable feeding speed.

As the blank is fed over an arcuate path transversely of the abrading surfaces of the tool rings and the latter are rotated at suitable cutting speed, the rough grinding ring I9 rst removes a roughing cut from the blank, followed by a finishing cut by the ring I8. Rings of various abrasive materials, cutting characteristics and dimensions, relative to each other, may be selectively and accurately associated, by means of the described construction, to provide a lens blank generating tool capable of performing simultaneously a plurality of grinding operations on the blank with a high degree of precision and rapidity of operation, so as to effect a substantial economy and improvement in the accomplishment of such work.

The present method is described in the above description of the construction and operation of a preferred mechanism for carrying it out, and as explained also in my said copending joint application, it provides for the performance of a plurality of simultaneous grinding operations to both rough and nish grind the blank while the latter remains undisturbed in its mounting on its carrier, so as to afford a rapid, precise and economical way of accomplishing such work.

The present invention covers a multiple layer or laminated grinding ring or wheel having the layers suitably graded as to grit size and speed of cutting, and preferably, with means for delivering coolant continuously to the lens blank surfaces over areas thereon lying between the abrading surfaces of the grinding rings for the purpose of scavenging material removed from the lens blanks by the next preceding abrading ring, also any abrading material loosened from the grinding ring itself, so the next finer abrading ring, under which the work is to pass, may perform its fine abrading operation without interierence from foreign materials of a coarser grain. It will be understood, of course, that the present invention may be applied to abrading wheels and rings having external and internal abrading surfaces of various contoursin the plane of the axis of rotation of the abrading tool.

It will thus be seen that the invention accomplishes its objects and while it has been herein disclosed by reference to the details of a preferred embodiment, it is to be understood that such disclosure is intended in an illustrative, rather than a. limiting sense, as it is contemplated that various modifications of the construction and arrangement of the parts will readily occur to those skilled in the art, within the spirit of the invention and the scope of the appended claims.

I claim:

1. In apparatus for grinding curved surfaces on lens blanks, mirror blanks and the like, the combination of a rotatable tool holder of hollow hemispherical form mounted for rotation about its axis, a tool seat on said tool holder in the plane of the greatest diameter thereof, means associated with said rotatable tool holder for feeding coolant continuously to the tool seat on said tool holder, said means including a bore through the spindle whereon the tool holder rotates and ducts through said tool holder connecting said bore with said tool seat, and an annular tool secured to said tool seat comprising a plurality of grinding rings having internal abrading surfaces of materials graded progressively as to cutting speeds and grit size, spacer rings separating said grinding rings, said grinding rings and said spacer rings being arranged side by side along said axis and having their bores centered thereon, said annular tool being provided with internal passages aligned with the ducts in said tool' holder to supply coolant continuously to the ground surfaces of work pieces between sad grinding rings for scavenging and cooling said Work pieces and said grinding rings as said work pieces are fed transversely of said annular tool.

2. The method for generator grinding of curved surfaces on lens blanks, including successive and simultaneous rough and finish grinding, in one operation, comprising the steps of rotating at suitable grinding speed a multiple grit progressively graded laminated grinding ring, and presenting simultaneously lens blanks to the grinding ring, over an arcuate path, to effect a feeding of the lens blanks across the laminated grinding ring for the purpose of generating finish ground surfaces on the lens blanks.

3. The method for generator grinding of curved surfaces on lens' blanks, including successive and simultaneous rough and iinish grinding, in one operation, comprising the steps of rotating at suitable grinding speed a multiple grit progressively graded laminated grinding ring arranged to scavenge loose material from the ground surfaces, and presenting simultaneously lens blanks to the grinding ring, over an arcuate path, to effect a feeding of the lens blanks across the laminated grinding ring for the purpose of generating finish ground surfaces on the lens blanks.

4. The method for generator grinding of curved surfaces on lens blanks, including successive and simultaneous rough and nish grinding, in one operation, comprising the steps of rotating at suitable grinding speed a multiple grit progressively graded laminated grinding ring with vent openings for circulating coolant to scavenge loose material from the ground surfaces, and presenting simultaneously lens blanks to the grinding ring, over an arcuate path, to effect a feedingvof the lens blanks across the laminated grinding ring for the purpose of generating iinish ground surfaces on the lens blanks.

ARTHUR J. HOLMAN.

(References on following page) The following references are of record ln the REFERENCES CITED le of this patent:

UNITED STATES PATENTS Number Name Date Wood Nov. 18, 1890 Davis Sept. 25, 1906 Winn Nov. 28, 1911 Wall et al May 25, 1915 Hollands Apr. 10, 191'7 Ames Oct. 16, 1917 MacGregor Jan. 6, 1920 Taylor Dec. 27, 1921 Taylor Dec. 27, 1921 Taylor Dec. 27, 1921 Number Number 

